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BBD to weber conversion problem

I have an 89YJ automatic, previous owner replaced the engine with an overbored 4.2 out of an 85 which runs great. He removed the cat, pulse air. The CTO with those 5 vac nipples was not connected at all. We had the charcoal cannister break, purge cap broke off and replaced it from one out of an XJ [unknown year], still had problems so I rebuilt the BBD, ran better but still would not idle and stalls when slowing down for lights and stop signs. Tough in traffic... At any rate I put one of the weber 551 kits in today and it runs, about the same as it ran with the BBD. I also replace the two rubber grommets for the PCV in the front and vent in the back. The vent is connected to the K&N filter. I also bought all new vac lines from the parts store and started replacing the to no avail. Some questions, what is "manifold" vacum and what is "ported" vacum. Am I fighting the computer here. Those two valves on the firewall, green one is supposed be manifold vac and the tan one is supposed to be ported vac, are not connected though one was with the BBD and was connected to the base of the carb under the old choke. Will replacing the CTO gain me anything ?? Do I need to do the nutterbypass on this. We don't have emissions testing here but I still plan on putting the cat back in and I would like the O2 sensor to work but not at the cost of putting the bbd back in. I tried hooking the vac lines up in various configurations due to my lack of understanding the manifold and ported vacs. The weber has two vac hookups, one in the front that I plugged the PCV into and the other on the side under the electric choke. Are either of them ported vacum ? This vacum stuff is driving me nuts, all I want it to do is run....

Reply to
Rich Pierson
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Hoo boy, where to start?

Ok, forget the O2 sensor, it will have zero effect on anything without the stock carb on there.

Then get the computer dead! It has gone into 'limp home' mode and has clamped down on the timing. I find it easiest to just add two new wires when doing the 'Nutter' bypass. I hook the orange and purple wires at the distributor directly to the orange and purple wires at the ignition module.

You then can forget all about 99% of the vacuum lines. None of the vacuum switches or any other emissions part will be in the loop. That includes the sol vac unit that was on the BBD to step up the idle when the tranny is put in drive. You just have to up the curb idle a bit to make up for it.

An XJ canister???????

I don't think that will work at all and could be half your headaches. Does it 'look' the same as the one you took out? If it has the same purge valve on it, then it might function ok, but the XJ ones I have seen didn't have that purge valve on top. (the purge valve is the part with the small vacuum line going to it)

A manifold vacuum is a nipple that sucks when the engine is idling. A ported vacuum is a nipple that only sucks when the throttle is opened.

The CTO valve controls vacuum. It has two ports on it that only allow vacuum to pass between them when the engine is hot. This is needed for proper EGR and charcoal canister operation.

Both the EGR and the canister purge valves are 'turned on' using a ported vacuum source routed through the CTO valve. They then only function when hot and at speed.

The PCV valve goes to a large manifold vacuum nipple. Just before it goes into the manifold, it needs a T fitting to pick up the charcoal canister purge line.

Then you need to tag the timing advance to vacuum. Your mileage may vary, but I get the best performance with the timing advance hooked into the same 'ported' vacuum line that goes to the CTO and controls the EGR valve. You T it in before the CTO or just where it comes out of the carb.

Here are a couple links that explain it fairly well:

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All I have working on mine is a large manifold vacuum nipple for the PCV and canister purge lines, a small manifold vacuum line for the air filter flaps to avoid iced carbs and a ported vacuum line for my timing advance and to feed the CTO which turns on my EGR valve and canister purge valve to allow the canister to purge into the PCV system.

Hope some of this helps,

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Rich Piers>

Reply to
Mike Romain

Thank Mike, OK, did the bypass and it fired right up and after about 2 min the idle seemed to calm down at 500rpm which is the fastest we could adjust the webers idle control screw into. It did not stall when going into drive or reverse so maybe we are almost there. Still idles a bit rough but I think my vac is still hosed up wrong. I pulled the charcoal cannister out and cleaned the filter [somehow I doubt AZ carries them in stock]. Son is putting on a new steering stablizer so right now so I'm in here with more questions and staying out of his way. The cannister has the exact same markings on it as the one in the link picture. So I am 'assuming' that it should work.

I can take out the two vacs on the fire wall, done. How can I eliminate that CTO ?? Do I want to, not really sure it even works, looks original. I was thinking of picking up a vacumn tree. The way I see it all I need is vac advance for the distributor and that should be ported, yes.

PCV into the base of the weber Purge signal from ported vacumn Purge line from manifold vacumn Line from cannister to gas tank Vent line from the carb bowl to the cannister

The vac resevoir is also not connected, does that get manifold or ported vacumn. We're getting there :-) I was a bit ticked as I could not find my amphenol tool to take the connector on the ignition control module apart. Got all the connectors in my amphenol kit but do you think I could find the $#%($ tool.

The weber has one vac stem on the side, near the valve cover, is that considered 'ported' or unported ?? Mike Romain wrote in news: snipped-for-privacy@sympatico.ca:

Reply to
Rich Pierson

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